Teixeira's OPS has declined for four straight years. It was, as you note, .807 last year. He is now a below average first baseman making over $20 M per year, which he will continue to do for several years. He is, in short, an economic millstone around the Yankees' neck.
Derek Jeter is finished. Yes, he had a .791 ops last year, after years of .743 and .710 before that. He could be expected, were he healthy, to revert to the mean, as players almost always do. His defense cost the Yankees 15 runs, or two games in the standings, last year. Coming off a broken ankle, he will get few infield hits and will be even more of a lawn ornament than previously. He is, in short, washed up, while still drawing a hefty paycheck.
Teixeira, Jeter, and A-Rod are the reasons the Yankees are playing such notables as Brennan Boesch, Vernon Wells and Francisco Cervelli on a daily basis.
Their 8-6 record is a fraud, shortly to be exposed. They are averaging 3.5 runs per game when not playing Cleveland. Absent the two games in Cleveland and discounting the three runs that scored on a dropped fly ball, the Yankees, despite some fine pitching at the outset, have been outscored by 9 runs.